1. Field of the Invention
The present invention relates to a musical tone synthesizing apparatus which simulates the non-electronic wind instruments and the like.
2. Prior Art
Conventionally, Japanese Patent Laid-Open Publication No. 63-40199 discloses an apparatus capable of synthesizing the sound of a non-electronic musical instrument by use of a simulation model which simulates the tone-generation mechanism of the non-electronic musical instrument.
In case of the wind instrument, when the resonance state is established between the non-linear vibration of a reed which is produced by the breath pressure applied thereto and the vibration of the compression wave of air which is produced in the resonance tube by non-linear vibration of the reed, the musical tone is produced from the wind instrument.
The most basic simulation model of a wind instrument such as clarinet includes a non-linear amplifier simulating the reed operation and a bi-directional transmission circuit simulating the resonance tube in which the compression wave of air propagates.
In this model, the output signal of the non-linear amplifier propagates through the bi-directional transmission circuit and is reflected at its terminal portion corresponding to the terminal portion of the resonance tube. Then, the reflected signal propagates through bi-directional transmission circuit and is fed back to the non-linear amplifier. In this manner, the simulation model of the tone-generation mechanism of the non-electronic wind instrument is embodied by the signal operation carried out by a closed-looped circuit including the non-linear amplifier and the bi-directional transmission circuit.
Additionally, the simulation model of the wind instrument which has plural tone holes for controlling a tone pitch is known. In this model, the simulation circuit for the wind instrument's tube includes plural bi-directional transmission circuits each simulating the path in which the compression wave of air propagates, junction units each simulating the scattering of compression waves at each point of the tube where each tone hole is made and a terminal circuit simulating the terminal portion of the tube. More specifically, the bi-directional transmission circuits and the junction units are connected together in the cascade-interconnection manner. In addition, the delay time of the first bi-directional transmission circuit corresponds to the path of compression wave between the reed and the first tone hole; the second bi-directional transmission circuit corresponds to the path of the compression wave between the first tone hole and the second tone hole; . . . the last bi-directional transmission circuit corresponds to the path of the compression wave between the last tone hole and the terminal portion of the tube. The last bi-directional transmission circuit is terminated by the terminal circuit including a low-pass filter simulating the acoustic loss of the terminal portion of the tube and an invertor simulating phase inverting phenomenon which is caused when reflecting the compression wave of air.
In each junction unit, the predetermined operation including coefficiency multiplication and the like is carried out on the signal output from a neighboring bi-directional transmission circuit, and the result of the operation is sent to a neighboring bi-directional transmission circuit. Each coefficient used for multiplication carried out by junction units are predetermined based on the shape of the tube and tone hole. In addition, each coefficient of the above mentioned operation is controlled in response to the finger operation applied to each tone hole.
The reflected signal from each junction unit or the terminal circuit is fed back to the non-linear amplifier. Thus, the signal is repeatedly circulating through the loop including the non-linear amplifier, junction unit and the terminal circuit. Since, each of the coefficients used in the junction units is controlled in response to the open/close state of each tone hole, resulting that the transmission frequency characteristic is varied in response to open/close state of each tone hole. More specifically, the primary resonance frequency is determined by the total delay time including the first delay time and the second delay time. In the case where at least one tone hole is opened, the first delay time is produced by the output signal of the non-linear amplifier to be propagated to the junction unit corresponding to first opened tone hole, while the second delay time is produced by the reflected signal of the junction unit to be fed back to the non-linear amplifier. Herein, the first opened tone hole designates the tone hole which is opened and is most nearly positioned by the reed. On the other hand, in the case where all of the tone holes are closed, the first delay time is produced by the output signal of the non-linear amplifier to be propagated to the terminal circuit, while the second delay time is produced by the reflected signal of the terminal circuit to be fed back to the non-linear amplifier. The transmission frequency characteristic has a plurality of peak portions each corresponding to each of the several resonance frequencies including the primary resonance frequency and its higher harmonic frequency to be produced when performing the non-electronic instrument. In addition, one of the paths through which the signal is circulating is selected by controlling each coefficient used in each junction unit, resulting that the transmission frequency characteristic of the resonance circuit is controlled. Thus, the pitch of the synthesized musical tone is controlled.
However, the conventional musical tone synthesizing apparatus needs a plurality of the junction units when synthesizing the musical tones produced by the non-electronic wind instrument having a plurality of tone holes. Thus, there is a problem in that the large-scale hardware is necessary in order that the musical tone synthesizing apparatus can synthesize such musical tones. In addition, when synthesizing the musical tone by use of the software operation, there is a problem in that a long operating time is needed for synthesizing the musical tone and consequently the musical tone cannot be obtained at real-time basis. On the other hand, in the performance of the non-electronic wind instrument, the tone pitch can be changed over between the basic tone pitch corresponding to the substantial tube length and another higher harmonic tone without changing the open/close state of tone hole. However, the musical tone synthesizing apparatus cannot control the generation of musical tones including the basic tone and its another higher harmonic tones such as to be produced by non-electronic wind instrument.